1. Field of the Invention
The present invention relates to an electrodeless lighting system, and more particularly, to an electrodeless lighting system capable of facilitating light distribution for achieving lateral lighting and a wider range of lighting and simultaneously improving lighting efficiency.
2. Description of the Background Art
In general, an electrodeless lighting system using microwaves is a device for emitting visible light and ultraviolet light upon applying microwave energy to an electrodeless plasma bulb. The electrodeless lighting system has a longer life span than that of incandescent lamp or fluorescent lamp which is generally used, and has higher lighting effect
FIG. 1 is a sectional view showing a structure of a conventional electrodeless lighting system.
As shown therein, in the conventional lighting lamp system, a high voltage generating unit 2 for raising a common AC voltage to a high voltage is installed at one side in a case 1, and a magnetron 3 for generating microwave by a high voltage supplied from the high voltage generating unit 2 is installed at the other side of the case 1.
And, a wave guide 4 is installed inside of the case 1 and communicates with an output portion 3a of the magnetron so that microwave generated by the magnetron 3 passes through the wave guide 4. An exit 4a of the wave guide 4 is exposed out of the case 1 through an aperture of the case 1.
In addition, a rotary shaft 5 is rotatably coupled at a shaft hole 4a formed at a central portion of the wave guide 4 in a vertical direction. A bulb 7 filled with a material which emits light by microwave energy is installed at an upper end portion of the rotary shaft 5 protruding outwardly through the exit 4a of the wave guide 4. A bulb rotating motor 8 having a motor shaft 8 connected to the rotary shaft 5 in the wave guide 4 by a connection pipe 7 is installed at a lower end portion of the rotary shaft 5 outside the wave guide 4 in order to rotate the rotary shaft.
And, a mesh-structured resonator 9 having a predetermined height (H) is coupled to the exit 4a of the wave guide 4, which is positioned outside the case 1, encompassing the bulb 6. The resonator 9 blocks leakage of electromagnetic waves introduced through the wave guide 4 and simultaneously passes light emitted from the bulb 6. A reflector 10 is fixed around the resonator 9 to cover the outer side of the resonator 9 in order to reflect light which has passed through the resonator 9 after generated in the bulb 6.
The resonator 9 is designed to use a TE mode (Transverse Electric mode). Because only one basic mode is used, intensity of an electric field is strongest at a central portion of the resonator 9. Accordingly, the bulb 6 is installed at a central portion (h) of the resonator, where the intensity of the electric field is strongest.
In addition, a cooling fan assembly 14 including a fan motor 11, a cooling fan 12 and a fan housing 13 having an outlet 13a is installed at a lower side of the case 1 so as to cool the magnetron 3 and the high voltage generating unit 2.
And, an inlet 13b through which external air is sucked by rotation of the cooling fan 12 is formed at the fan housing 13. A plurality of discharge openings 1b are formed at an edge of an upper surface of the case 1 so that the air sucked through the inlet 13b can be discharged outside by way of the high voltage generating unit 2 and the magnetron 3.
Non-described reference numeral 15 in the drawing is a dielectric mirror.
An operation of the conventional electrodeless lighting system constructed as above will now be described.
When power is applied, a high voltage is generated in the high voltage generating unit 2, the generated high voltage is supplied to the magnetron 3, and microwave is generated by the applied high voltage in the magnetron 3.
The generated microwave is radiated into the resonator 9 through the wave guide 4, a material within the bulb 6 is electrically discharged by the radiated microwave to thereby generate light by plasma, and the generated light is thrown to the front by being reflected by the dielectric mirror 14 and the reflector 10.
And, the bulb rotating motor 8 rotates the rotary shaft 5 so that a temperature of the bulb 6, which is raised by the light generated in the bulb 6, does not exceed a predetermined temperature
In addition, the fan motor 11 installed at a lower portion inside the case 1 rotates to rotate the cooling fan 12. External air sucked through the inlet 13b by the rotation of the cooling fan 12 flows through the outlet 13a, cools the high voltage generating unit 2 and the magnetron 3, and then is discharged outside the case 1 through the discharge opening 1b formed at the upper surface of the case 1.
However, in the conventional electrodeless lighting system constructed as above, in order to make lateral lighting and wide-area lighting in a basic mode, a distance (h) between a central portion of the bulb 6 and the dielectric mirror 15 is to be designed to be longer. As the distance (h) therebetween becomes long, a height (H) of the resonator should be designed to be longer, and, if the size of the resonator 9 becomes great in such a manner, a higher mode has to be used. If the higher mode is used, a loss of the microwave becomes great in the basic mode, thereby causing not only a size increase of the entire electrode lighting system but also remarkable deterioration in lighting efficiency. Accordingly, the conventional electrodeless lighting system has a problem in that light distribution for achieving lateral lighting and wide-area lighting is difficult.
In addition, if the higher mode is used as described above, a matching characteristic of frequency becomes different from that in a basic mode. Accordingly, a shape of a feeding hole formed at the exit of the wave guide, for outputting microwave into the resonator becomes very complicated, thereby making a design of an electrodeless lighting system for frequency matching complicated.